Gas turbine engines are known and when used on aircraft typically include a fan delivering air into a bypass duct and into a compressor section. Air from the compressor is passed downstream into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.
Turbine rotors drive compressor and fan rotors. Historically, the fan rotor was driven at the same speed as a turbine rotor. More recently, it has been proposed to include a gear reduction between the fan rotor and a fan drive turbine. With this change, the diameter of the fan has increased dramatically and a bypass ratio or volume of air delivered into the bypass duct compared to a volume delivered into the compressor has increased. With this increase in bypass ratio, it becomes more important to efficiently utilize the air that is delivered into the compressor.
One factor that increases the efficiency of the use of this air is to have a higher pressure at the exit of a high pressure compressor. This high pressure results in a high temperature increase. The temperature at the exit of the high pressure compressor is known as T3 in the art.
Due to the increased T3 temperature, the last stage (the aft most stage) of a high pressure compressor in the turbine engine, as well as the compressor rotor rim, can experience temperatures beyond the typical temperature capabilities of the compressor stages and the compressor rotor rim. The additional heat experienced can cause a decrease in the lifespan of compressor components such as the last stages of the compressor.
To address this T3 systems utilize a compressor on-board injection (COBI) system that receives cooled air from a heat exchanger in a cooled air system and uses the cooled air to cool the last stage of the compressor and the compressor rotor rim. Known cooled air systems include air losses due to circuitous flow routes and complex mixing between the heat exchanger and the compressor on-board injection (COBI) system.